On this page you can find information on tropo propagation. A executable programm can
help you calculating the possibilities of making a contact. It calculates both for a line
off sight contact and for tropo scatter contacts.

First some explanation what troposcatter is.

Troposcatter Propagation: from an
article of G3YGF

The Mechanism of Troposcatter

Troposcatter uses the weak, but
reliable, reflections that can be obtained from the dust particles, clouds and refractive
index variations that occur in the atmosphere 1000 to 50,000 ft above sea level. This
mechanism can be used for working DX reliably over distances of many hundreds of miles. A
brief illustration of the relevant part of the atmosphere is shown inthe picture

Air density decreases with height, and reaches one-third
of its sea level value at about 30,000 ft. The refractive index of the atmosphere depends
on such properties as temperature, density (pressure), humidity or the presence of water.
Variations in any of these properties can scatter the signals. The scattering process is
more efficient at lower altitudes where the atmosphere is denser. Turbulence associated
with the weather can have marked effects on the signal levels and characteristics. In
practice, this mechanism is used by pointing both antennas along the great circle path
between the two stations at as low an angle of elevation as possible. The two beams will
intersect in a common volume of the atmosphere near the center of the pathSee the
picture

Propagation will be line-of-sight to the common volume from the transmitter. A very
small fraction of the Power passing through this volume will then be scattered in all
directions by the irregularities in the atmosphere. This power then propagates by
line-of-sight to the receiver. The height of the bottom of this scattering volume will
depend on the path length, and to some extent on the horizons of the sites, but will be
typically 2000 ft on a 60-mile path, and 30,000 ft on a 300-mile path. The loss in the
scattering process is usually so large that the equipment is unlikely to have enough spare
capability to overcome the extra losses introduced by any additional obstructions in the
path. The path loss increases by about 10 dB for every degree of horizontal angle at each
station. On paths over 60 miles the increase is about 9 dB for every extra 60 miles of
path length. The choice of a site with a good horizon is vitally important; it can make a
difference of several hundred miles in the obtainable range.